1.0 Field of the Invention
The present invention relates generally to orthopaedic implants and, more particularly, to bone plates and bone plate assemblies which may be implanted in various parts of the human body to stabilize bone fractures.
2.0 Related Art
Orthopaedic surgeons frequently encounter bone fractures which require surgical stabilization with implants including metal bone plates having a variety of shapes. Difficulties in the repair of these fractures include insufficient assistants in the operating theater and fractures that are difficult to reduce (i.e., returning the fractured bone segments to their proper positions) and hold. Conventional bone plates may be generally classified as either "compression plates" or "one-third semi-tubular plates." Both types of plates are available in a variety of shapes, for use in stabilizing various bones, and typically include a plurality of interior holes (i.e., spaced apart from the edge of the plate and surrounded by metal) which accept bone screws to secure the plates to the fractured bone segments. Furthermore, both types of bone plates may be somewhat curved, as seen in an end view, to accommodate the cross-sectional shape of the particular bone. Compression plates are relatively thicker and the included interior holes are typically "compression holes" having either one or two ramps which extend longitudinally toward the center of the hole from the outer to the inner surface of the plate. The compression holes cause the bone plate to move longitudinally relative to the bone screws used to secure the plate, as the screws are tightened. The one-third semi-tubular plates are relatively thinner and typically include straight-through holes without the foregoing longitudinally extending ramps.
Both compression plates and one-third semi-tubular plates have been widely and successfully used to stabilize bone fractures. However, the implantation of either type of plate may be problematic for the surgeon in certain instances as illustrated in the subsequent discussion regarding a typical procedure for implanting conventional bone plates.
The bone fracture is approached through a standard incision. Soft tissue such as periosteum, muscle, arteries and veins are partially stripped from the bone to allow visualization of the area and to allow temporary placement of bone clamps and the implantation of the bone plate or plates. The surgeon commonly faces situations in which he or she struggles to achieve alignment of the fractured bones with the use of bone clamps, only to have to remove the same clamps securing the reduction in order to position and attach the bone plate. A bone clamp may be used to reduce the fracture by applying it directly around the fracture, if the fracture pattern is amenable, i.e. such as an oblique fracture. The fracture may also be reduced by placing clamps above and below the fracture site and applying traction against each end until the bone segments are realigned. Either method requires stripping of soft tissue off of bone and additional soft tissue trauma, and potential devitalization of bone.
After the fracture is reduced, the bone segments must then be held in place to allow removal of the clamps to permit placement of the bone plate. In some instances, the fracture may be secured by placing a bone screw across the fracture site, but this is only feasible if the fracture is oblique and is not excessively comminuted (i.e., broken into more than two pieces). However, the screw head may be disposed in an area that interferes with placement of the bone plate, creating additional difficulties. Commonly, the surgeon must try to add and subtract clamps as he or she implants the bone plate. This procedure may be compounded by the bending and contouring of the plate that is usually necessary, requiring repeated engagement and disengagement of the clamps. Not only is this procedure difficult, frustrating and time consuming, it may result in a loss of fracture alignment and creates additional soft tissue stripping and trauma. Once the bone plate is finally properly positioned, it is secured with bone screws, x-rays are performed, and the wound is closed.
In view of the foregoing disadvantages associated with the surgical implantation of conventional bone plates, a need exists for an improved bone plate which reduces operating room time, open wound time, anesthesia time and minimizes the risk to the patient.